Questions tagged [beam]
Questions about the theory and applications of structural elements designed to resist bending.
163
questions
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Deflection and stress in a freely rotating beam
How do I calculate the deflection and stress of a beam that is rotating freely (for example in space) when a moment is being applied to it, for example by rocket motors at the ends of the beam?
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1answer
40 views
Problem while solving for the moment of a cantilever beam
As in the first image,
Moment at any point between C and B should be 0.
But when I try to solve it by substituting equal and opposite forces at end C so that anti-clockwise moment of $F(l-a)$ and ...
0
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0answers
46 views
Problem with cantilever beam and yield strength
Hey, I make a project in which I use a cantilever beam with distributed equal load across the whole beam and I'm using the formulas above to calculate the displacement, moment...
My specifications ...
0
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1answer
38 views
Maximum I-beam girder S12x31.8 span
Does 200lb/in of load on a S12x31.8 over 15 feet seem reasonable? I'm having a tough time trusting the numbers.
Two story house with an attic as below. Dotted lines show load bearing walls W1 and W2. ...
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0answers
29 views
moment of area in c section
I have been trying to solve a problem that asks for the max shear and normal stress in cantilever beam.My problem is in regards to the 1st moment of area of the beam section.Not sure how to upload ...
1
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3answers
50 views
Buckling vs. Yielding Failure of Columns
As I have been working through examples of construction projects, I've noticed that in nearly every case of a structural column (sample size considers only homogeneous material columns, no composite ...
1
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1answer
37 views
What criteria must apply for torsional effects on this beam to be ignored in calcs?
I'm interested in how to work out whether torsional effects can be ignored or not, in calculating the adequacy of a given steel beam in the following idealised eccentric scenario.
Or, equivalently, ...
0
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1answer
52 views
Modification of Beam Equation for Thin Sheet
I am trying to determine the modulus of elasticity (Young's Modulus) for a rigid paper sheet. The issue I am having is that my results for the Young's Modulus change depending on what orientation (...
0
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2answers
59 views
Pin joint system displacement question
A pinned system comprising bars of the same material and cross-sectional area is subjected to a vertical load P.
I am required to form a relationship between FAB and P.
The first part of the ...
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0answers
26 views
How to write the equilibrium stress equations for a hollow, rectangular beam?
I have a system consisting of a hollow, rectangular cantilever beam (pictured below). I'd like to write the equilibrium stress equations à la the Cauchy Stress notation.
How do I account for the ...
2
votes
1answer
58 views
Why are variations zero on the endpoints of a beam?
On Wikipedia derivation on Timoshenko beam equation we arrive at this:
$$ \delta U = \int_L \left[-M_{xx}\frac{\partial (\delta\varphi)}{\partial x} + Q_{x}\left(-\delta\varphi + \frac{\partial (\...
2
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1answer
84 views
How to analyze a bent beam: Stress concentration?
I am analyzing a beam, that has a bend in it. Intuitively and inspecting FEA results using a linear solver, there is a stress concentration at the bend of this I-beam.
When I was learning about ...
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1answer
103 views
Calculating area moment of inertia for a beam with underslung plate?
In a number of designs, a beam will have an underslung welded plate attached, as shown below:
In this sketch, a symmetrical standard steel beam/column of dimensions H1 x B1, with web and flange ...
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0answers
51 views
Rotational bending in Timoshenko beam theory
The Wikipedia article on Timoshenko beam theory says:
The model takes into account shear deformation and rotational bending effects,
I am familiar with shear deformation, but what is meant by "...
1
vote
1answer
58 views
simple supported Beam deflection question involving two point loads and a UDL
so i was given a problem by my mechanical principles teacher to work out the max vertical deflection of a simply supported beam with two point loads one a distance of 5.3 away from A and another 5.9 ...
0
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1answer
89 views
Along which direction is the area moment of inertia taken in bending moment equation?
Is it in the same direction of the applied load or in the co-planar perpendicular direction to the load applied?
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1answer
64 views
MSC Nastran - BAR3/4 elements - can't assign any properties
I'm modeling a pipe in Patran, and I'd like to try bar3 and bar4 elements.
I assing the properties CBEAM to my geometry, but when I create the mesh, Patran tell me bar3 and bar4 don't support that ...
2
votes
3answers
66 views
Do internal / external stresses affect modal frequency?
Imagine a cantilevered beam, fixed on one end and with a tension line connecting the other end to ground (e.g. perpendicular to the length of the beam).
If I increase the tension, does the modal ...
0
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3answers
98 views
Composite beam- increase in bending moment due to reinforced steel
While trying to solve this question and using the flexure formulas of bending for composite beams I obtained a lower value of moment for steel than for aluminum.How is that possible?
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3answers
88 views
Reaction Forces on a Beam
I'm new to beams and I'm struggling to find the correct vertical reactions forces at support C and E.
The correct answer is 8.58 kN for $V_c$ and -3.58 kN for $V_e$
However, when I ...
0
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2answers
86 views
How to get the bending moment for tie member?
How to get the bending moment for tie member? For the tie member, there is no uniformly distributed load and concentrated load, right? How to get the bending moment? The tension force was found to be ...
3
votes
3answers
85 views
Why does concentrated shear force on a beam influence the whole beam?
This might be a silly question but can someone explain how this shear force on the right side of the beam causes Qy throught the whole beam?
I understand it mathematically but not conceptually so I ...
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0answers
186 views
Simple beam deflection of cantilever beam
Recently I had need to prove the beam deflection equation for a simple cantilever beam with a point load at the end. The equation would be in reference to the Euler-Bernoulli theory taught in most ...
0
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2answers
430 views
Simple beam with cantilever ends
I'm trying to find the maximum bending moment and deflection for this symmetrical simple beam. The formulae I can find, deal with either cantilever beams with one fixed end, or continuous beams ...
0
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2answers
172 views
Statically indeterminate fixed-pinned beam problem
F=32KN; Mf1=60KN-m; Mf2=-58KN-m; g=30KN/m I need to solve this using Force method. Find the reaction at the pinned end.
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2answers
800 views
Stiffness of a cantilever beam
I am working on calculating the stiffness of a cantilever beam by applying a distributed load. I wanted to ask if the distribution of the load on the beam effects its stiffness.
For eg., if I apply a ...
1
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1answer
250 views
Can bending moments for a combination of loads on a simple beam, be calculated by adding the individual B.M. of each load?
This problem is about bending moment of a simple beam subject to a mixture of 4 or 5 UDLs and point loads. The beam is assumed to be rigid enough that deflection of the combined load is "small".
...
2
votes
2answers
98 views
Indeterminate beam with a guide at each end
I've been battling with a statics question (as attached) and can't for the life of me figure it out.
I've attempted removing the left side guide joint so then there are only 3 reactions and it should ...
0
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2answers
463 views
Shear force and bending moment for continuous span
It's given that L1 = 5m, L2 and L3= 7.5m, w = 8.9kN/m , I am asked to find the bending moment using these coefficient.. Prior to this , i need to have the value of shear force first.Shear force = ...
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0answers
37 views
Possible improved approaches to 6mx3m moment-resisting frame with eccentricity+torsion, in advance of detailed engineer discussion
I'm putting a steel frame in, to "open plan" the rear of a brick cavity-wall terrace house in the UK, which will then have a single storey extension added behind it.
I have already retained a ...
0
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1answer
352 views
Shape Functions of beam element with 3 nodes (quadratic element)
For a two node beam element there are four shape functions for four degree of freedom:
For a straight three node beam element how shape functions are?
Please note that beam is straight and not ...
0
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1answer
34 views
Big Beam LVL or Glu Lam load capacity to support a gymnast
I need help knowing if I am selecting the correct wood beam.
The load will be all near the center and a 250 pound man will be doing pull ups on it. I would estimate a 1,000 pound dynamic load to be ...
2
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0answers
65 views
What is the optimal shape of a beam subject to three point bending?
Assume we have a beam with density $\rho$ that is subject to three-point bending according to the image above. The beam cross section is rectangular with the variable height $H(x)$ and constant width $...
1
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1answer
78 views
Calculation of natural frequency in a hinged beam
What I tried: Using the conjugate beam method to find deflection and hence stiffness of the beam, but I am unable to find reactions in the conjugate beam.
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0answers
318 views
Derivation of Bimetallic Strip Stress in Roark's Formulas
I am trying to understand some analytic expressions given in the handbook Roark's Formulas for Stress and Strain for bimetallic strip stresses. Namely, Roark's Formulas give the formulas
$$\text{...
3
votes
1answer
222 views
Torsional rigidity D vs torsional rigidity factor k vs torsion constant J
I have a physics background so apologize my ignorance.
I'm confused by the constants $D$, $\kappa$, and $J$ when it comes to torsion of beams. From what I understand $\kappa$ and $J$ are the same ...
1
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1answer
18 views
Supporting flexible square plate of uniform density in equilibrium with only 4 rolling contacts placed along the square's diagonals
Consider a flexible square of uniform density with vertices (0,0), (0,1), (1,0), (1,1). I need the 4 coordinates for rolling contacts along the diagonals that will stably support it. Someone could ...
3
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1answer
162 views
How to measure the unbraced length of lateral torsional buckling for negative moment in a W-shape steel beam?
I have a W-shape steel beam that is fixed-fixed and the top flange is fully braced for lateral torsional buckling. The negative moment at the end controls the design and there is no lateral bracing ...
3
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4answers
1k views
How does stiffness/rigidity affect the bending moment of a beam
My question may sound silly as it’s mainly good sense but I may be mixing things up.
Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other ...
2
votes
2answers
98 views
Why two identical beams without being pinned together will share half of the bending moments?
As shown above, two identical rectangular beams are placed and NO pinned together. I know each beam has its own neutral surface but why they carry half of the bending moments? I thought the bending ...
1
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1answer
37 views
What's the second moment of a T beam with a heel? [closed]
The second moment of area of a rectangle is $I_{yy} = \dfrac{bh^2}{12}$
b : base
h : height
What is the second moment of area of a T beam like this one?
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0answers
56 views
How much (uniformly distributed) weight can this L beam support without bending? [closed]
As you can see in the picture, the L beam is 1in x 1/2in x 1/8in thick x 72in long and is made of ASTM A36 steel. It's bolted onto a vertical upright on both ends.
What is the maximum uniformly ...
2
votes
1answer
67 views
Abaqus Failure for I-Beam Section in Major direction only
For my 4th year dissertation in Civil Engineering I've got to investigate the difference between BS5950, Eurocode 3 and ABAQUS failures. The only thing is, in the BS5950 and Eurocode 3 the failure can ...
0
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2answers
135 views
Resulting torque on the cross section
I have trouble solving part A of the question. I thought the resulting torque would just be 10k * L of the beam.
0
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1answer
60 views
Which container orientation, if any, can hold more weight?
These are cross sections of identical shipping containers, except one is rotated 45 degrees. The cross sections are squares, 3 meters to a side. I drew dashed lines to show where they're suspended by ...
2
votes
2answers
211 views
Neutral axis in canteliver beam at support
First, I thought the neutral axis would just be the y bar which can be obtained from the centroid of the cross-section but is different. I have tried letting the net moment at the wall = 0 and the ...
3
votes
1answer
111 views
Should one use multiple elements through the thickness with multiple materials?
To get realistic results from a FEM calculation, it is common (or so I've been taught by someone who may not be up to date) to use at least four or five elements through the thickness of a beam or ...
2
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0answers
226 views
How to add Beam cross section properties to imported mesh in Ansys?
Ansys Workbench 17.1
I have a mesh that was imported from Abaqus into Ansys but the beam cross section data is missing. As a result the structural model omits the beam elements.
How do I access the ...
1
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2answers
555 views
Deflection of a cantilever beam composed of separate (not bonded) planks
In the case of a simple cantilever beam having a uniform shape and being loaded at its end - the calculation of the deflection at any point along the beam is well known.
What happens if we split it ...
1
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2answers
126 views
Is is possible to use singularity function to expresse the horizontal forces ?
I know how to translate torques and vertical forces into singularity functions, but may i also express the horizontal forces with singular function? if yes then what would be that expression?
Here ...
